1. Field of the Invention
This invention relates to a system for heating the interior of a motor vehicle and includes a combustion heater for burning fuel in a heat exchanger in order to heat the air supplied to the vehicle interior and/or liquid in the vehicle in the cooling circuit of the engine.
2. Description of Related Art
To heat a motor vehicle interior independently of the vehicle engine, conventionally, combustion heaters are combined with a conventional heating system which is based on heat exchange with the coolant circuit of the engine. The combustion heater can burn fuel from the vehicle fuel tank in order either to directly heat air which is delivered into the vehicle interior or to heat coolant in the coolant circuit which then delivers heat to the vehicle interior via one or more heat exchangers.
German Patent Application DE 199 02 050 A1 discloses a heat exchange which is equipped with an electrical heating device. Heating by means of an electrical heating device, especially with the engine off, is possible only for a very short time since otherwise the vehicle battery is overloaded and restart of the engine is endangered.
German Patent Application DE 198 57 240 A1 discloses a heater which can be operated both with liquid fuel and also with an electrical heating element in the form of a heating coil which can be integrated into the heat exchanger of the heater. The heating coil must be inserted during installation into the vehicle heater or its heat exchanger and contacts established, a complex procedure. Since in the area of the heating coils a liquid heat exchange medium is circulated, both the heating coil and also its contacts must be provided with waterproof insulation. This greatly increases the costs of one such combined heating device.
The primary object of the invention is to devise a motor vehicle heating system with a combustion heater which can be operated as flexibly as possible and still has simple installation, low costs, good efficiency and low installation space requirements.
This object is achieved in accordance with the invention by a heating system with a combustion heater for burning fuel in a heat exchanger in order to heat the air supplied to the vehicle interior and/or liquid in the vehicle in the cooling circuit of the engine, whereby an electrical heating device is integrated on or in one wall of the combustion heater in order to supply heat to the air or liquid to be heated. By integrating an electrical heating device into the combustion heater, the combustion heater can be operated much more flexibly and with higher heat output without significantly increasing the installation space required, the installation requirements, and the overall costs.
The invention is detailed below using the attached drawing which schematically shows one embodiment of the invention.